The invention relates to a display device having a first substrate, on which pixel electrodes and correspondingly therewith active elements are provided, a display material and a second substrate, the first and second substrata being disposed on opposite sides to each other with respect to the display material sandwiched therebetween.
The invention is used in a display device in which an input function is incorporated.
More specifically, the present invention is used in a flat-type display device with an input function in which a liquid crystal material, an EC material or the like is used. Such a display device with an input function is suitable for use as a device for the purpose of education or office automation, such as a combination of a CRT display device with a light pen, wherein information displayed on the screen can be selected at its displayed position and sent to another device, or wherein information of a display position on the screen can directly be input.
A liquid-crystal type display device in which an input function with the aid of light is incorporated is known, for example, from Japanese Patent Applications Laid-Open Nos. 60-195519 and 61-6729.
In the conventional crystal display device shown, for example, in FIG. 11, scan electrodes 6a, 6b, . . . are provided on a substrate which is disposed on one side of a liquid crystal material 2. Another substrate disposed on the other side of the liquid crystal material is provided thereon with active elements 1a, 1b, . . . , signal electrodes 3a, 3b, . . . , photo-sensitive elements 7a, 7b, . . . , scan electrodes 4a, 4b, . . . for the photosensitive electrodes, and read-out electrodes 5a, 5b, . . . . In this case, a display operation is performed by driving the active elements 1a, 1b, . . . and an input function is established by the use of the photo-sensitive elements 7a, 7b, . . . .
In another example of the conventional devices shown in FIG. 12, a substrate disposed on one side of a liquid crystal material 2 is provided thereon with an electrode of a transparent conductive material. Another substrate disposed on the other side of the liquid crystal material is provided thereon with active elements 1a, 1b, . . . , scan electrodes 8a, 8b, . . . for the active elements, photo-sensitive elements 7a, 7b, . . . , and read-out electrodes 4a, 4b, . . . for the photo-sensitive elements.
With the conventional display device of the above-described type, a substantial number of electrodes such as the signal electrodes, the scan electrodes for the photo-sensitive elements and the read-out electrodes must be provided on the same substrate in addition to the active elements and the photo-sensitive elements. The process for the fabrication of the display device is therefore complicated and the product yield rate is therefore low. in the case of the conventional display device shown in FIG. 11, since the electrodes for the display function and those for the input function are separated from each other, this display device has a disadvantage that a circuit for driving the above electrodes is complicated.
Display devices similar to the above-described conventional display devices are also disclosed in Japanese Patent Applications Laid-Open Nos. 56-104387, 56-85792 and 59-94736 and Japanese Patent Application Publication No. 57-49912.
All the conventional display devices disclosed in the above published documents have been designed for monochromatic picture display, and none of the documents mention a technology for color picture display.